1. Field of the Invention
The present invention relates to an electrostatic charge image developing toner.
2. Description of Related Art
An electrostatic charge image developing toner (hereinafter, also simply referred to as “toner”) for use in electrophotographic image forming is demanded to have reduced thermal energy in fixation for the purposes of an increase in printing speed and saving of energy of an image forming apparatus. In response thereto, a toner with a much better low-temperature fixability is demanded.
With respect to such a toner, for example, a toner is known into which an amorphous polyester and a vinyl resin, and a crystalline polyester having so-called sharp meltability that results in a rapid reduction in elasticity in a narrow temperature region are introduced as binder resins (see, e.g., Japanese Patent Application Laid-Open No. 2004-309996). In the toner described in Japanese Patent Application Laid-Open No. 2004-309996, rheological property is regulated and a viscoelastic behavior is controlled to thereby allow excellent low-temperature fixability to be realized.
With respect to such a toner, for example, a capsule toner is also known into which an amorphous polyester and a crystalline polyester are introduced as binder resins and which is capsulated (see, e.g., Japanese Patent Application Laid-Open No. 2008-268353). In the toner described in Japanese Patent Application Laid-Open No. 2008-268353, the resins having a chemical structure similar to each other are used to thereby control compatibility, and the toner is capsulated to thereby achieve excellent low-temperature fixability and heat resistance.
The toner described in Japanese Patent Application Laid-Open No. 2004-309996, however, has the following problem: when crystallization of the crystalline polyester is insufficient, the glass transition temperature of the toner decreases to cause heat resistance to be insufficient. The toner also has the following problem: when melt viscosity of the toner is too low, an image is not properly separated from a fixing member in high-speed printing, namely, so-called separation failure occurs. Furthermore, when the vinyl resin and the crystalline polyester are included in binder resins, these may largely differ in terms of polarities and chemical structures thereof to thereby cause a large crystal domain to be likely formed. If a large crystal domain is formed in an image after fixation, roughness occurs on the surface of the image, also resulting in the problem of deterioration in uniformity of glossiness of the image.
On the other hand, while the toner described in Japanese Patent Application Laid-Open No. 2008-268353 is excellent in both of low-temperature fixability and heat resistance, the toner has the following problem: melt viscosity of the toner is so low that separation failure occurs in high-speed printing.
As described above, there is room for improvement in the prior art from the viewpoint that a toner sufficiently having all of low-temperature fixability, separation property, high-temperature storage property, and uniformity of glossiness of an image fixed is realized.